LOGFILE logfilename # to set where your logfile livesYou need to use \ not / as the directory separator in the logfile name. The logfile must live on your local disk -- analog doesn't fetch it from across the network. There's a sample logfile supplied with the program.
There's a list of basic commands later in the Readme. Also there are a few to get you started in the configuration file already, but there are lots of others available. You can read about all the commands in the section on customising analog.
There is one other way to give options to analog, via command line arguments, given on the command line after the program name. These are just shortcuts for configuration file commands.
If you want to compile your own version of analog (it's written in C), or just to read the source code, it's available from the analog home page. (It's the same source code for all versions). There are instructions about compiling on another page.